TCP memory usage, ethernet driver

[Antti P Miettinen]

> > Then a question: about how much memory does a TCP connection take?
> 
> What are you concerned about code, data/bss or heap usage?

I'm just wondering how much data is needed per active connection. Is
it neglible so that applications could more or less freely use
parallel streams or should application design try to minimize number
of connections and to multiplex data through few connections? It seems
that a file descriptor could take something like 52 bytes which is
IMHO neglible, but does TCP need more? How many streams could I
support with the recommeded 256k heap?

I'm not yet familiar enough with RTEMS to know whether the data comes
from heap or is statically allocated based on some config parameter. I
know the answer to the question might not be very straight forward but
I'm just looking for a very rough figure.

Another question.. the 68360 ethernet driver seems to re-enable BDs
upon (at least some) transmit failures. Is this correct behaviour? The
ppc 860 driver does not do this.

Hmm.. yet another. What is the context for the ethernet driver
interface calls? I suppose they are called with the network semaphore
held (start updates if_flags as does tx task)?

Antti Miettinen
Nokia Networks